How to use llvm-gcc-4.2 on Yosemite / El Capitan

llvm-gcc-4.2をYosemite (10.10) / El Capitan (10.11)でも使用する方法

Upgrading from command line tools from Xcode 4.6 (or 4.5)

• If you have installed command line tools from Xcode 4.6 (or 4.5), you still have /usr/llvm-gcc-4.2 even after your Macs are upgraded to Yosemite.
• Installing command line tools (by xcode-select --install, required) will install /usr/include, which is used by /usr/bin/llvm-gcc-4.2. You can also have /usr/include/c++/4.2.1 used by /usr/bin/llvm-g++-4.2.
• If you want to keep some compatibility, you should not remove /usr/llvm-gcc-4.2.
  • The warning couldn't understand kern.osversion '14.0.0' can be ignored.

New installation

Warn: I have not confirmed if this method works or not.

• Download Command Line Tools (OS X Mountain Lion) for Xcode - April 2013 from https://developer.apple.com/downloads/ (You need an Apple ID).
• Open the dmg and extract Packages/DeveloperToolsCLI.pkg using unpkg.
• Copy usr/llvm-gcc-4.2 to /usr.
• Symlink /usr/llvm-gcc-4.2/bin/ to /usr/bin/.

Anyway

There are yet no ways to have pure gcc-4.2, which has been removed in Xcode 4.3. The effort to maintain it in MacPorts and Homebrew has reached limit (because of upstream license GPLv3).

Additional note

• clang++, which is the official compiler on Mavericks and Yosemite, has an option -stdlib=libstdc++.
  • Using this, you can link your C++ program against libstdc++ instead of libc++.
  • Of cource, -stdlib=libstdc++ cannot be used with -std=c++11 (on OSX) because this libstdc++ is quite old.
• Due to this feature, apple still keeps /usr/include/c++/4.2.1 even in their latest command line tools.
• When they drop this feature, this trick will stop to work.

iostream

• Even this code results in compile error.

#include <iostream>
int main(int argc,char **argv){
  std::cout<<1<<std::endl;
}

• To avoid the error, use llvm-g++-4.2 -mmacosx-version-min=10.7.
• Acknowledgement: http://stackoverflow.com/a/12133504/2641271

El Capitan

• Due to SIP, sadly you cannot have /usr/llvm-gcc-4.2 anymore. But /Library/SystemMigration/History/Migration-*/QuarantineRoot/usr/llvm-gcc-4.2/bin/llvm-gcc-4.2 (or elsewhere as long as inside directory structure is kept) is safe!